Femtosecond laser-induced backward transfer (LIBT) offers a promising route for direct metallization of transparent substrates while limiting thermal damage, yet the conditions governing film continuity, oxidation state, and electrical behavior in copper deposits are not well established. Here, copper was transferred from a bulk donor onto ultra-clear soda-lime glass using a 1030 nm, 208 fs Yb-based solid-state laser, with donor-receiver gap, fluence, and scan speed systematically varied. Deposited films were characterized by SEM, 3D optical profilometry, Raman spectroscopy, XPS, and four-point probe resistivity measurements. A 40 µm donor-receiver gap yielded the most uniform, continuous coverage. Low fluence produced discontinuous nanoscale clusters, while higher fluence generated denser, continuous tracks, though with greater Cu2O and CuO alongside metallic copper, confirmed by Raman and XPS. Films combining continuous coverage with minimal oxidation showed the lowest as-deposited resistivity (23 × 10⁻⁵ Ω·cm), while discontinuous or heavily oxidized films showed markedly higher values. Subsequent annealing in 5% H2/Ar reduced the LIBT-formed oxides—verified via Raman, high-resolution XPS, and Cu LMM Auger analysis—and promoted grain coalescence, densifying the films and lowering resistivity further to 7.21 × 10⁻⁵ Ω·cm. These findings establish clear structure-property-process relationships for femtosecond LIBT of copper, supporting fabrication of high-quality, low-resistivity Cu films.

Color marking on transparent glass by conventional laser processing is often limited because glass has weak visible absorption and typically produces a narrow range of dark or neutral surface appearances. In this work, color marking on borosilicate glass was achieved using nanosecond laser-induced backward transfer (LIBT) of brass with varying laser power (50-90 W) and scanning speeds (100-1500 mm/s). A controllable color palette of pale yellow, brown, reddish-brown, and blue-green tones was produced and quantified using CIE L*a*b* analysis, revealing three distinct color regimes within the process window. Scanning electron microscopy showed a morphological evolution from sparse nanoparticles at low energy to agglomerated clusters at intermediate energies, and droplet-dominated deposits at high energy. Energy-dispersive spectroscopy confirmed the presence of Cu, Zn, and O in the layers, while X-ray photoelectron spectroscopy identified oxidized Cu-Zn, with Cu2O, CuO, and ZnO as the main oxide phases, which varied with processing conditions. The observed color responses are attributed to the combined effects of oxidation, deposited-layer morphology, surface coverage, and wavelength-dependent optical attenuation. A color prediction model was developed using experimentally measured CIE Lab*, constrained by observed oxide chemistry and morphology evolution to reconstruct the principal color regimes across the process map. The model successfully reproduced color tones observed in the experimental color regimes, yielding a mean ΔE of 11.18 and 87.5% of predictions within ΔE < 20, indicating similar color regimes. These results demonstrate that brass-based LIBT can be used as a controllable route for producing oxide-mediated color patterns on transparent glass surfaces.

In-situ micro-rolling at elevated temperatures during Directed Energy Deposition (DED) improves build quality by providing plastic deformations. However, experimentally characterising the deformations and understanding mechanisms behind these improvements remains challenging and thus necessitates thermo-mechanical finite element analyses (FEA). Previous FEA studies in the literature have focused on single-track and thin-wall multi-layer cases, and a more realistic multi-track, multi-layer scenario has not yet been the subject of a comprehensive study. This study develops and validates an FEA framework for in-situ rolled DED in a representative case of three-track, three-layer Ti-6Al-4V deposition, achieving thermal predictions with 90

Laser-assisted machining with ultrasonic vibration (VLAM) offers efficient processing of difficult-to-cut materials by simultaneously exploiting intermittent cutting and laser heating. However, the simultaneous influence of laser heating and vibration on the machining process remains poorly understood. Therefore, this paper proposes a novel 2D finite-element-based coupled thermo-mechanical model of the VLAM process to gain better insight into the process mechanisms by predicting stresses, temperatures, and forces. The model is developed in Abaqus/explicit by coupling material constitutive behavior, thermal effects, and vibration kinematics, enabling accurate prediction of cutting forces. Experimental validation using magnesium AZ31B alloy demonstrates good agreement between predicted and measured forces and the accuracy of the model is observed to be about 5 %. The VLAM model is also compared with the conventional machining (CM), laser-assisted machining (LAM), and vibration-assisted machining (VAM) models. The VLAM model shows the highest temperature and the lowest forces among the CM, LAM, and VAM models, which correlates well with the experimental literature. This work demonstrates the effectiveness of the VLAM process as compared to the other processes. The developed model provides a framework that can be extended to other difficult-to-cut materials for enhanced process understanding.

Atom probe tomography (APT) enables three-dimensional, near-atomic-scale compositional analysis of nanomaterials; however, its application to individual nanoparticles (NPs) remains limited due to the complexity of specimen preparation, including lift-out procedures and precise apex shaping. In this work, we investigate ultrafast laser micromachining of NP-embedded resin composites to develop a protocol for the direct, site-specific fabrication of APT specimens without the need for lift-outs. Finite element simulations of laser processing reveal that increasing the NP concentration significantly enhances optical absorption, expanding the heat-affected zone from 5 to 20 mu m within the resin composite. As a proof of concept, tip arrays containing embedded spinel ferrite NPs are laser micromachined on a resin half-grid with minimal thermal damage and subsequently polished using focused ion beam milling. APT analysis of these specimens yields a high number of detections from both the resin matrix and the NPs, enabling reconstruction of distinct oxide isosurfaces and detailed compositional mapping. Overall, this study highlights the potential of laser-based preparation as a practical alternative route for enabling APT analysis of nanoparticle-embedded systems.

Laser cleaning is one of the most efficient and environment-friendly rust cleaning methods. The removal of the corrosion layer from steel surfaces by nanosecond pulsed lasers usually causes discolouration of the surface. By proper selection of laser parameters, this discolouration can be avoided without compromising the material removal rate. In this work, a study on the treatment combination of laser power, scan speed, pulse repetition rate, and hatch distance on the colour of the laser-cleaned surface and the material removal rate is conducted via response surface methodology using a central composite design. The factors and interactions that significantly affect the response were identified by ANOVA. The model was experimentally validated and the parameter combination that gives the highest material removal rates with a shiny surface was identified with ∼ 90 ^3 /s to 0.4 mm ^3 /s in the current range of parameters. The maximum material removal is observed to be at laser power between 7.5 - 10 W and hatch distance between 45-50 m when the scan speed is 875 mm/s and PRR is 50 kHz. However, the feasible region that can create a surface with the same metallic colour as a polished steel surface is extremely narrow when compared to the full range of the parameters used in the study.

Ti6Al4V is a difficult-to-machine material due to its high strength, low thermal conductivity, and low elastic modulus. Laser-assisted machining (LAM) has great potential to enhance the cutting performance of Ti6Al4V. However, the selection of optimum parameters is challenging due to the complexity of LAM process. In this research, response surface methodology (RSM) is used for parameter optimization and to understand the influence of cutting speed, laser-tool gap, and laser power on cutting forces during LAM of Ti6Al4V. The experiments are designed using central composite design (CCD). Analysis of variance (ANOVA) and 3D response surface is examined to analyze the interaction of cutting speed, laser-tool gap, and laser power on cutting forces. A regression model is prepared to achieve minimum cutting force based on process parameters. The experiments are conducted to validate the regression model and the model accurately predicts cutting forces. The combination of low cutting speed, large laser-tool gap, and high laser power has shown minimum cutting forces. Moreover, the optimal parameters have achieved lower tool wear and minimum chip serration due to lesser chip adhesion and lower built-up layer (BUL) on tool surface. The outcomes suggest that selection of optimal parameters would enhance the cutting performance of Ti6Al4V.

In characterization methods like Atom Probe Tomography (APT) and Atomic Force Microscopy (AFM), a comprehensive grasp of the thermal dynamics of nanotips under fast-pulsed laser irradiation is essential. This work presents a simulation study of laser interaction with nanotip specimens for applications in APT. Extensive analysis of the heating and cooling processes in silicon nanotips is conducted through the finite element method. The effects of different experimental conditions are incorporated in the model, including the specimen geometry, standing electric field, and cryogenic base temperature. Finite-difference time-domain (FDTD) simulations are used to calculate the light absorbed at different locations in the specimen, which is then used to determine heat input. It was observed that less than 5

In-situ rolling in directed energy deposition has shown improvements in deposited part quality. These improvements are driven by high-temperature material deformation. Experimentally capturing high-temperature deformation aspects is challenging. The modelling approach requires simultaneous consideration of rolling and deposition aspects. Therefore, a fully coupled thermo-mechanical model is developed for single-bead cases. It combines the frameworks of heat source motion, corresponding element activations, and thermo-mechanical rolling deformations in a single analysis. Johnson–Cook plasticity model is incorporated for yield stress evolutions with thermo-mechanical deformations. Experimental validations are done using temperature and rolling load measurements in laser deposition with 90% and 84% respective accuracies. Thermal predictions of the offset-dependent rolling temperatures are made, and the chilling effects of rolling are identified to be spatially and temporally confined on the deposited bead. The induced plastic strains on the bead for given compressions are quantified, and corresponding rolling loads are predicted. Plane strain condition with triaxial stress formation at the rolling location offers new insights on the relief in longitudinal stress, even with compressive load in the build direction, due to restriction in the plastic flow of material in the longitudinal direction with Poisson’s effects. Thus, this work comprehensively understands the hot deformation effects of in-situ rolling and its parameters through finite element analyses in single bead cases.

Femtosecond laser micromachining (FLM) is an effective technique for generating functional surfaces and microfeatures on glass substrates. However, FLM of glass in ambient air is prone to micro-cracks, debris, and thermal damage in the machined region leading to poor surface quality. The ambient medium used in FLM significantly affects the quality of the machined surface. In this study, FLM of glass is carried out in four different ambient media; KOH, HF, DI water, and ethyl alcohol to compare their effects on the surface quality. The glass substrates were submerged 1 mm below the free surface of liquid media and 300 mu m wide channels were fabricated by scanning the laser beam of diameter 40 mu m and 209 fs pulse duration at variable pulse energies. The experimental results show FLM in KOH solution exhibits better surface quality than HF, DI water, and ethyl alcohol. The surface roughness values of microchannels obtained in the KOH solution were the minimum, measured to be 1.125 mu m at 15 mu J. Microcracks were observed in the other three media which were most prominent in ethyl alcohol. FLM of glass in KOH is a promising approach for minimizing roughness and thermal damage without much loss of surface integrity. These findings have implications for the development of glass microfluidic devices and other applications that require precise and functionalized glass surfaces.

This paper investigates the different material removal mechanisms that occur during quasi-continuous wave (QCW) fiber laser drilling using millisecond pulses on stainless steel 304 samples and studies their effect on hole quality. A high-speed imaging camera is integrated with an in situ laser setup to capture the material removal during the laser drilling process. Based on high-speed camera images, four different material removal mechanisms were observed, which include vaporization, melt-expulsion at the hole entrance, melt-ejection at the hole exit, and explosive boiling. Vaporization occurs at all fluences beyond a certain threshold and is followed by melt-expulsion after a particular laser fluence value, leading to material deposition at the periphery of the hole entrance. Explosive boiling occurs at higher fluences beyond a certain threshold, resulting in material removal in the form of vapor and liquid droplets. Besides, the high pressure involved in explosive boiling also causes melt-ejection from the hole's exit, leading to the formation of a through hole. Furthermore, it is observed that an assist gas plays a crucial role in effectively displacing the molten material, thus generating a uniform and through hole. This sequential evolution of mechanisms offers valuable insights into delineating the roles of each mechanism and developing process maps for the dimensions and quality of mu-holes produced.

This study explores nanosecond laser welding of 1.2 mm thick soda-lime glass substrates using a 1064 nm pulsed fiber laser (100 ns pulse duration) with an aluminum (Al) foil interlayer positioned at the glass-glass interface. The Al interlayer enables localized melting and resolidification, facilitating strong bonding. Laser power (20-80 W) and scan speed (50-400 mm/s) were systematically varied to optimize joint quality and minimize interfacial defects. Microstructural characterization revealed the formation of a continuous interfacial reaction layer comprising Al2O3 and Al-Si-O compounds, confirmed through X-ray photoelectron spectroscopy. Mechanical testing showed that peak shear strength was achieved under optimum power and scan speeds, where balanced melting and oxidation promoted mechanical interlocking and chemical bonding. The results establish a strong correlation between processing parameters, interfacial chemistry, and joint performance, offering insights into tailoring laser parameters for defect-minimized, high-strength glass-to-glass welding using metal interlayers.

Treadle pumps are promising manual pumping alternatives for low gravitational suction and delivery head conditions. The operation of a treadle pump comprises dynamics of the motions of the centre of mass of the operator, treadles, pistons with piston rods and fluid columns. The present article presents a comprehensive steady-state analytical model for the operation of a treadle pump, with the aim of designing key pump parameters and achieving maximum discharge for the given farm field conditions. The analytical model of the pump was developed by formulating the equations of motions of the centre of mass of the operator, treadles and pistons with piston rods. The model integrates the dynamics of the operator’s motion with the treadle pump system, making it a uniquely comprehensive model. The validation of the discharge flow rate of the numerical model confirms good agreement with experimental results, with a deviation of 5–10

Single-crystal (SC) nickel-based superalloys provide improved high-temperature strength, and resistance to creep, fatigue and oxidation, compared to equiaxed and columnar-grained components due to their higher solid solution strengthening, precipitation hardening and the absence of grain boundaries. However, the SC nickel-based superalloys are 'difficult-to-cut'. To enhance the machinability, a concept of laser-induced surface damage (LISD)-assisted machining is being studied. Laser surface modification (LSM) experiments were been performed by employing the design of experiments (DoE) strategy L18, OA (orthogonal array). The LSMed geometries were characterized to identify various laser-induced surface defects including solidification cracks, microcracks, micropores, microstructural changes, phase changes, recrystallization, and deformation. Further, parametric interactions and optimization of the process parameters were performed to manufacture a larger LISD layer. The parameter-structure-property relationship was derived systematically and the mechanisms of LISD on the SC nickel-based superalloy were described in details. The results indicate that the LISD increase with an increase in laser power followed by a decrease in scan speed and beam diameter. LISD geometries possess 1 % to 4 % of crack density and lower hardness of around 27 % than the base metal. Slot milling experiments were then conducted on the LISD specimens, which showed up to a 40 % reduction in cutting forces when compared to untreated specimens. It is evident that this methodology can be adopted to further improve the machinability of various difficult-to-cut materials.

We present Daksha, a proposed high energy transients mission for the study of electromagnetic counterparts of gravitational wave sources, and gamma ray bursts. Daksha will comprise of two satellites in low earth equatorial orbits, on opposite sides of earth. Each satellite will carry three types of detectors to cover the entire sky in an energy range from 1 keV to >1 MeV. Any transients detected on-board will be announced publicly within minutes of discovery. All photon data will be downloaded in ground station passes to obtain source positions, spectra, and light curves. In addition, Daksha will address a wide range of science cases including monitoring X-ray pulsars, studies of magnetars, solar flares, searches for fast radio burst counterparts, routine monitoring of bright persistent high energy sources, terrestrial gamma-ray flashes, and probing primordial black hole abundances through lensing. In this paper, we discuss the technical capabilities of Daksha, while the detailed science case is discussed in a separate paper.

Laser micromachining can serve as a coarse machining step during sample preparation for high-resolution characterization methods leading to swift sample preparation. However, selecting the right laser parameters is crucial to minimize the heat-affected zone, which can potentially compromise the microstructure of the specimen. This study focuses on evaluating the size of heat-affected zone in laser annular milling, aiming to ascertain a minimal scan diameter that safeguards the inner region of micropillars against thermal damage. A computational model based on the finite element method was utilized to simulate the laser heating process. To validate the simulation results, a picosecond pulsed laser is then used to machine the micropillars of Al and Si. The laser-machined samples were subjected to surface and microstructural analysis using Scanning Electron Microscope (SEM) and Electron Backscatter Diffraction (EBSD) scans. The length of heat affected zone obtained from simulations was approximately 6 mu m for silicon and 12 mu m for aluminum. The diameter of micropillars formed with laser machining was 10 mu m for silicon 26 mu m for aluminum. The core of the pillars was preserved with less than one degree of microstructural misorientations making it suitable for further processing for preparing specimens for techniques like APT and TEM. For silicon micropillars, the preserved central region has a diameter of 6 mu m and for aluminum its around 20-24 mu m. Additionally, the study determines the minimum scan diameter that can be achieved using the given laser machining setup across a range of common materials.

This study investigates the influence of KOH as an ambient media for efficient cutting of glass samples using a femtosecond laser and found that the surface quality can be enhanced with minimal burrs.

In fabricating passivated emitter and rear contact (PERC) solar cells, creating small openings on the SiN x coated silicon substrate to establish metal contacts necessitates using a nanosecond pulsed green laser for ablation. However, the thermal nature of laser ablation poses a challenge. Excessive nitrogen diffusion from SiN x into the silicon substrate can compromise the electrical performance of solar cells. Therefore, this study aims to comprehensively understand how laser parameters impact the electrical properties of such solar cells. PERC solar cell precursors were initially fabricated by ablating the SiN x layer at four laser fluences, each corresponding to different regimes: solid, liquid, vapor, and phase explosion. Subsequently, various optical, chemical, and electrical characterizations were conducted on the solar cell precursors. Complete PERC solar cells were also fabricated to measure quantum efficiency (QE). In the solid regime, SiN x removal is precise, with minimal thermal damage, resulting in a nitrogen concentration of approximately 0.15%. Photoluminescence count and carrier lifetime are notably higher by 21% in the solid regime compared to the explosive regime. The QE measurement at 984 nm quantitatively assesses rear-side recombination losses. Notably, 26% of the area exhibits a 56% QE in the solid state, while this number drops to around 22% in the explosive state. This decline can be attributed to increased thermal damage in the explosive regime, which augments recombination centers and diminishes the solar cell performance. PERC solar cells ablated in the solid regime showcase lower subsurface damage, superior electrical characteristics, and higher performance than those ablated in the explosive regime.